Rotary and longitudinal shock absorber for drilling

ABSTRACT

A rotary and longitudinal shock absorbing apparatus with an mandrel therein is connected to a drill string assembly to absorb abnormal longitudinal shocks and abnormal torsional shocks by cooperating hydraulic and mechanical means, while allowing communication of drilling fluid through the body of the apparatus. The construction of the apparatus is such that torque shock absorbing action is independent of the longitudinal shock absorbing action and the apparatus provides balanced internal and external pressure to permit its operation at all levels of hydraulic pressure.

This application is a 371 of PCT/US98/04750 filled Mar. 11, 1998 andalso claims one fit of Provisional No. 60/040,963 filed Mar. 12, 1997.

TECHNICAL FIELD

This invention relates to an energy absorbing device for tubularmembers, specifically to such devices for arresting both longitudinaland torsional shocks on tubular members used in drilling operations.

BACKGROUND ART

In the process of rotary drilling of wells, a variety of abnormal forcescan cause stress on the drill string members which comprise the drillstring assembly. If these abnormal forces or loads occur repetitively,they can cause failure of the drill string assembly. Down hole vibrationand torque have long been associated with bit-failure and drill stringfailure. These various events are described as stick/slip, bit whirl,bit bounce, and bottom-hole-assembly (BHA) whirl and resonance. Althoughhighly cost-effective, the development and deployment of new slimholedrilling techniques has been hampered by mechanical problems resultingfrom bit whirl and stick-slip problems.

Directional drilling programs have introduced other problems associatedwith various shock fatigue factors. The use of downhole motors fordriving the drill bit has also been delayed because of vibrationalproblems associated with the forces described herein.

Although these events have long been recognized as a cause of drillstring failures and a variety of tools have been developed to limit oreliminate these shocks, no generally acceptable device has beendeveloped which is capable of absorbing the damaging overload stressesfrom repetitive longitudinal and rotary shocks.

A number of prior art devices have been proposed to absorb shocks in adrill or pipe string. For example, U.S. Pat. Nos. U.S. Pat. No.2,212,153 to Eaton (1940) (relating to sucker rod vibrations only), U.S.Pat. No. 2,756,022 to Sturgeon (1956), 3,871,193 to Young (1975), U.S.Pat. No. 3,998,443 to Webb (1976), 4,600,062 to Teng (1986) and U.S.Pat. No. 4,844,181 to Bassinger (1989), each describe devices orcombinations of devices to absorb axial or longitudinal shock, yet allowtorque transmission to the drill string. U.S. Pat. No. 3,998,443 to Webb(1976) discloses an arrangement to absorb both longitudinal and torqueshock, but limited excessive torque by translation of the torque intolongitudinal movement. Thus, this patent did not independently absorbboth torque and longitudinal shock in the drill string.

DISCLOSURE OF THE INVENTION

The present invention provides an shock/vibration-absorbing tool thatwill effectively act to reduce or eliminate abnormal shocks from beingtransmitted through the drill string irrespective of the source of theshock. Abnormal energy can be imparted to the drill string by a numberof sources or causes. These energy loads can manifest themselves aslongitudinal movement in the drill string, or torsional movement in thedrill string, or both. The present invention provides a tool which actsintermediate the drill string and the bottom-whole assembly (BHA) or bitto allow progressively resistive longitudinal movement to absorblongitudinal or axial shocks as from bit bounce. Independently of thatfeature, the tool is designed to absorb abnormal rotation of the drillstring as from bit whirl. This invention thereby prevents this abnormalenergy from either source from propagating throughout the drill stringassembly. The tool consists of a mandrel attached through anintermediate assembly to the lower sub assembly which both absorbsunusual energy which is transmitted, yet permits continuous torque to betransmitted to the drill bit from the surface drive means.

If the source of the energy shock originates above the tool, the mandrelis compressively moved telescopically into the drive cylinder whichallows continued rotational movement, while simultaneously absorbing(through both mechanical and hydraulic means), the initial energyloading of the shock. The shock is dampened by the movement of themandrel into the annular space provided by the drive cylinder, connectorsub and compression cylinder which cooperatively and progressivelyresist the shock and the damaging movement of the drill string byresilient cooperating mechanical and hydraulic means.

If the source of the energy shock originates below the tool, the energyis transmitted to the tool which drives the lower sub and compressioncylinder up, causing compression of the lower resilient assemblies,which in turn move the compression mandrel against the hydraulic andmechanical energy absorbing means in the drive cylinder. The dampeningeffect of the present invention from both directions, and independent ofthe rotational energy which may be continued to be imparted the drillstring, realizes the long-desired but unobtained goal of a device whichabsorbs rotational and longitudinal shocks. The tool continues toprovide rotational energy which is required to maintain movement of thedrill bit on the well bottom.

A further object of this tool is to provide a tool in which thelongitudinal axial shock absorbing means is separate and apart from thetorque shock absorbing means.

A still further object of this tool is to provide a tool in which thelongitudinal shock means will address both light and heavy shock loads.

Another object of this tool is to provide a tool in which thetorque-shock absorbing means has the ability to absorb at least twocomplete 360° turns.

An additional object of this tool is to provide a tool for use withpolycrystalline diamond compact bits in which the torque-shock absorbingmeans will address bit whirl, both clockwise and counterclockwise.

Another object of this tool is to provide an energy absorbing device inwhich the pump-out or thrust means has a low effective piston area.

Another object of this tool is to provide a tool which will absorbabnormal energy conditions in the drill string to provide theelimination of excessive torque on drill string joints, which willlessen the need for excessive force in loosening joints upon recovery ofthe well string.

The transmission of energy through the tool is symmetrical whether thecompressive energy originates at the bit end of the tool or from abovethe tool. Since damage can be experienced to the mechanical top-driveunits from abnormal torsional shocks, the placement of theenergy-absorbing drive mechanism of the invention may be used to absorbabnormal energy being transmitted up the drill string to the drive unit.

Other objects and advantages of the tool will become apparent from aconsideration of the following description and the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1—A vertical section view illustrating a preferred embodiment in anuncompressed, but torqued, mode.

FIG. 1A—A vertical section view of the torque sleeve engagement of thedrive cylinder threads with mandrel splines.

FIG. 2—A vertical section view illustrating a preferred embodiment in acompressed mode.

FIG. 3—A vertical section view illustrating a preferred embodiment in acomprised and torqued mode.

FIG. 4—A cross-section view of torque and spline sleeve section.

FIG. 5—A illustration showing a cut-away section of the torque sleevesplines.

FIG. 6A—An illustration showing a preferred placement of inventionattached to a drill bit.

FIG. 6B—An illustration showing another placement of invention in themiddle of the BHA.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring to the drawings and in particular FIG. 1, the tool embodyingthe present invention is shown generally at 1 in an longitudinallyuncompressed, but fully torqued, view. The tool 1 is adapted to beplaced in the tubular string between a drill bit (not shown) and theremainder of the drill string which is connected to the drillingequipment at the surface. Accordingly, the tool 1 is fashioned withmandrel 2 with threaded box connection 3 to permit connection with thedrill string through normal connection which may be formed in a numberof different configurations well known to those skilled in the art.Mandrel body 2 is threadably connected to compression piston 37.Compression piston 37 is threadably connected to compression mandrel 17which is threadably connected to equalizing mandrel 32, permittingtelescoping longitudinal movement of such elements inside drive cylinder8, connector sub 14, neutralizing cylinder 33 and equalizing cylinder 34and lower sub 25. Lower sub 25 provides a threaded pin connection 26 forconnection to the drill bit or bottom hole assembly in manner well knownto those skilled in the art. Threaded pin connection 26 may also beconnected intermediate a drill collar, which is connected to a rotarydrill bit.

The tool 1 is provided with an axial flow passage therethrough to allowflow of drilling fluids through the tool without constriction. Mandrel 2is also provided with a shoulder 6 against which is fit wear ring 5 onwhich wear pads 4 are placed, all fabricated of hardened or wearresistant materials, such as 4340 steel, also well known to thoseskilled in the art of manufacture of down-hole tools to preventexcessive wear and allow the tool to be redressed after use and reused.

Mandrel 2 is telescopically engaged in the drive cylinder 8 which isconnected by connector sub 14 to compression cylinder 19. Mandrel 2 isthreadably connected by compression piston 37 to compression mandrel 17,and is free to slidably move from the up-impact face 16 to the top ofthrust bearing 13 which is permits engagement with light load Bellevillesprings 20 and heavy load Belleville springs 21. Movement of thecompression mandrel 17 relative to the compression cylinder 19 isrestricted by resilient members such as light load spring 20 and heavyload Belleville spring 21 which are stopped on Belleville supportshoulder 15′. The choice of resilient members may be varied to permitvariable resistance throughout the entire range of expecting operatingloading of the tool in the wellbore.

The connection between the mandrel 2 and the drive cylinder 8 is madeslideable by the cylindrical bearing surface carried on the mandrel 2against which a plurality of fluid seals 7, 7′ and 7″, which provide adynamic or sliding joint between the mandrel 2 and the drive cylinder 8to permit longitudinal movement of the mandrel 2 relative to the drivecylinder 8.

Fluid seals 7, 7′, and 7″ are elastomeric sealing elements fabricatedfrom nitrile materials, Teflon seals and elements containing brassinserts, respectively, which are configured in a manner well known tothose skilled in the manufacture and installation of seals in down-holetools. It may also be appreciated that alternative elastomeric sealmeans may be substituted for each of the seals described withoutdeparting from the spirit of the invention to provide a dynamichydraulic seal. Each of the sets of packer seal elements used in thepresent invention: fluid seals 7, 7′,7″; piston seals 77′, 77″;equalizing seals 36 36′, 36″; mandrel seals 31, 31′, 31″; and hydraulicseals 87, 87′, 87″ are each formed from the same materials and are eachintended to provide a sliding seal between the inner member and theouter member around each set. The neutralizer piston 23 is a slidingseal assembly permitting dynamic hydraulic sealing between thecircumferential exterior of the compression mandrel 17 and the interiorcircumferential surface of the neutralizing cylinder 34.

A down impact face 6 is formed between the lower edge of wear rings 5,stopped against the mandrel shoulder 6″ and the upper edge of drivecylinder 8. The mandrel is protected from excessive wear by wear ring 5which is faced with wear pad 4. Seals 7, 7′and fluid seals 7″ are set inthe upper portion of the drive cylinder 8 to provide a dynamic hydraulicseal between the mandrel 2 and the drive cylinder 8. Drive cylinder 8 isthreadably connected to connector sub 14 and encloses a torque sleeve11, thrust bearing 13 and upper torque resisting Belleville springs 27.Drive cylinder 8 is provided with inner torque threads 9′ to engage thetorque sleeve 11 and its outer torque threads 9.

As more fully disclosed in FIG. 1A, drive cylinder 8 provides multi-leadinner torque threads 9′ to engage the outer torque threads 9 on torquesleeve 11. Torque sleeve 11 has internally spline 12′ to accept theexternal splines 12 of mandrel 2 to provide transmission of rotationalenergy from the drive means for the drill pipe (not shown) to the drillbit through the shock absorbing apparatus.

Drive cylinder 8 is also be fitted with a fill ports 22′ to fill aninner chamber 15 formed therein with an incompressible fluid. Torqueresisting Belleville spring 27 and thrust bearing 13 encircle mandrel 2and are enclosed within the inner chamber 15 (formed by the drivecylinder seals at 7, 7′ and 7″ and the pistons seals at 77, 77′ and 77″on the neutralizer piston 23) to provide engagement of bottom of torquesleeve 11. The inner chamber 15 extends from the fluid seals 7, 7′ and7″ on drive cylinder 8 the piston to seals 77, 77′ and 77″ on theneutralizer piston 23 which slideably seal the tubular compressionmandrel 17 and the neutralizing cylinder 34. The inner chamber 15 isisolated from the well fluids surrounding the tool 1 in the well boreand is filled with gear oil, or other incompressible fluid. Annularneutralizer piston 23, which is slideably engaged between compressionmandrel 17 and neutralizer cylinder 34, dynamically seals inner chamber15 from the well fluids allowed to communicate through neutrlizing port24 to maintain the fluid within the inner chamber 15 at substantiallythe same hydrostatic pressure as the well fluid which surrounds the tool1. The equalization of interior pressure with exterior pressure preventsthe fluid seals 7, 7′ and 7″ and piston seals 77, 77′ and 77″ fromexperiencing substantial pressure differentials and permits slideableengagement between the mandrel 2 and lower sub 25.

As previously noted, external splines 12 are fashioned on the uppermandrel body which engage the inner splines 12′ of the torque sleeve 11.The outer surface of the torque sleeve 11 is fashioned with fast leadouter torque threads 9, as more fully described in the description ofFIGS. 1A, 4 and 5. As compressive forces are experienced in the drillstring from above the tool in the well bore, the energy absorbed by thetool 1 is transmitted to the mandrel 2 and thence to the compressionmandrel 117. Energy dampening is provided by the lower resilientmembers, springs 20 and 21 which are compressed against Bellevillesupport shoulder 15′ and against the hydraulic forces of the associatedcompression in inner chamber 15.

Similarly, abnormal torsional forces transmitted are absorbed by themovement of the torque sleeve 11 within the drive cylinder 8 which areresisted by the torque-resisting Belleville springs 27, the movement oftorque sleeve 11 and the hydraulic forces of the compression in innerchamber 15. As more clearly shown in FIG. 3 showing the tool 1 in fullcompression, inner torque threads 9 urge the torque sleeve 11 towardcompressive engagement with thrust bearing 13. These torque threads aredesigned to provide at least two complete 360° turns of the tool beforethe compression cylinder 19 will snub against the down impact face 6.Bit whirl, experienced when the bit has been released after sticking,causes drive cylinder 8 to turn at a rate relatively faster than mandrel2 moving torque sleeve 11 up and away from further compressiveengagement. A similar phenomenon occurs during milling operationsintended to cut or mill a window in the casing of the wellbore to allowdirectional drilling. The “biting” of the mill against the casing wallcauses abnormal torque to build up in the drill string causing the millto hop off the wall before completion of the mill job. The tool 1 of thepresent invention may also be used to allow abnormal torque experiencedby the mill to be absorbed while maintaining the mill at the casing wallpermit more efficient cutting operations to continue.

Torque sleeve 11 engages the outer surface of thrust bearing 13 whichallows smooth rotational engagement in compression between the torquesleeve 11 and the torque resisting Belleville springs 27, which arecarried on the connector sub 14. Connector sub 14 connects drivecylinder 8 with compression cylinder 19. Compression mandrel 17 isthreadably engaged with compression piston 37 and mandrel 2 and slideswithin compression cylinder 19. Compression piston 37 is also formedwith split-ring flow restrictor 18 which retards communicating flow ofthe incompressible medium between the portion of the inner chamber 15adjacent mandrel 2 and the compression mandrel 17. This space, whichextends from the fluid seals 7, 7′, and 7″ to the piston seals 77 foundon the neutralizer piston 23 permits dampening communication of theincompressible fluid. A second thrust bearing 13′ is disposed betweenthe light-load Belleville spring 20 and the lip of the compressionpiston 37. Light-load Belleville spring 20 abuts heavy-load Bellevillespring 21 which is also disposed around the compression mandrel 17 andinner the chamber 15 formed in compression cylinder 19.

The hydrostatic pressure differentials which may be experienced betweenthe inner chamber 15 resulting from compression of the tool 1 at variousdepths and with various pump pressures, and external fluids are balancedby neutralizer piston 23. Neutralizer piston 23 is formed by thecooperating dynamic piston seals 77, 77′, and 77″ between the exteriorsurface of compression mandrel 17 and the interior surface ofneutralizer cylinder 34. Neutralizing piston 23 slides on both surfaces.Neutralizer port 24 allows balancing of exterior pressure throughneutralizer port 24 with the interior pressure formed by the neutralizerpiston 23 and dynamic equalizing seals 36, 36′and 36″ which provide adynamic seal between compression mandrel 17 and the upper portion ofequalizing cylinder 33. Neutralizing cylinder 34 is threadably engagedto equalizing cylinder 33, which is threadably engaged with lower sub 25to provide a threaded pin connection for connecting the tool 1 to otherportions of the drill string or to the drill bit.

Equalizing cylinder 33 provides external equalizing ports 38 whichpermit exterior annular pressure to be balanced with interior pumppressure. Drilling fluids in the well annulus communicate throughequalizing port 38 and balance with the hydraulic pressure which isallowed to communicate through pump port 35 to the space formed betweenthe equalizing cylinder 33 and the equalizing mandrel 32 by theslideable engagement of mandrel seals 31, 31′ and 31″ between the innerwall of equalizing cylinder 33 and the equalizing mandrel 32. Thisequalizing mandrel is sealingly engaged in the lower sub 25 byadditional hydraulic seals 87, 87′ and 87″. These cooperating elementsprovide operability of the tool 1 at all pump pressure levels and at alldepths of operation.

It should be appreciated that the mandrel 2, drive cylinder 8, connectorsub 14, compression cylinder 19, neutralizing cylinder 34, equalizingcylinder 33, and lower sub 25 may be formed of any suitable number ofcomponent parts to enable their assembly and relative positioning insuch a telescoped relation as illustrated in FIG. 1 of the drawingswithout substantially departing from the spirit or intent of theinvention.

FIG. 2 is the tool shown in longitudinal compression. In normal use, thetool 1 is connected to the drill string intermediate the drill bit orbottom hole assembly and the drill collars. Drilling rotation moves themandrel 2 which turn the torque sleeve 11 and move it downward toincreasing resistance from the torque resisting Belleville spring 27.This continuous and vibration free transmission of torque to the drillbit.

As the drill string is rotated, mandrel 2 moves into the annular bore ofthe drive cylinder 8 by helical compression of the fast thread torquesleeve 11 against the torque resisting Belleville spring 27 and therebymoves compression mandrel 17 down. This helical compression by movementof the torque sleeve 11 continues until the down face 6 seats againstwear ring 5. The movement of the fast thread torque sleeve 11 isadditionally resisted or dampened by the incompressible fluid containedin the inner chamber 15. Longitudinal movement of the mandrel 2 into theannular bore of the drive cylinder 8 which is cooperatively engaged withthe connector sub 14 and thus to the compression cylinder 19 is furtherresisted and energy absorbed by the movement of the compression mandrel17 against the resistive force of the combined resistance of both thelight load Belleville spring 20 and the heavy load Belleville spring 21.All of the spring elements are moving against the compression of theincompressible fluid in the inner chamber 15 further dampening movementof the compression mandrel 17 which is connected to the lower sub 25 andthe remaining portion of the drill string or bit as may be required.These cooperating elements of the tool 1 resists the bit hopping up fromthe cutting surface and absorbs the longitudinal energy fromaccumulating and precipitating bit whirl as the energy is released tothe bit.

FIG. 3 is the tool shown in compression as both longitudinal andtorsional energy is distributed from the drive cylinder 8 throughout thetool 1. Torque sleeve 11 has moved through the drive cylinder 8, againstthrust bearing 13 to compress the torque resisting Belleville spring 27against the upper edge of connector sub 14. Simultaneously lowerBelleville springs 20 and 21 are moved into full compression and thecompressible fluid in the inner chamber 15 has driven equalizing piston23 against the upper end of the lower sub 25.

FIG. 4 is a top view of torque sleeve 11 engaged inside drive cylinder 8and engaging mandrel 2. As also previously noted, inner torque threads9′ engage the outer torque threads 9 torque on sleeve 11.

FIG. 5 is part frontal view of torque sleeve with cut-away disclosingexternal spliner 12 on the interior of the torque sleeve 11, andreflecting the torque threads 9 on the exterior of the torque sleeve 11.A plurality of circumferentially spaced fast-lead torque threads areprovided on the outer surface of the torque sleeve 11 to cooperativelyengage circumferentially spaced torque threads formed on the innersurface of drive cylinder 8. A plurality of circumferentially spacedspline seats are formed on the inner surface of torque sleeve 11 tocooperatively engage the splines formed on mandrel 2 to providerotational movement.

As previously noted, the apparatus is partially filled with aincompressible medium such as gear oil so that under normal drillingoperation loads the down-impact face 6 is not contacting the upper end6″ of drive cylinder 8.

FIG. 6 is a view of the invention showing the placement of the preferredembodiment in the drill string assembly. Drill string member 28 isprovided with a plurality of pony collars 29 to provide stability to thetool 1 which is shown with down impact face 6 indicating theuncompressed form. Drill bit 30 is. engaged in the lower end of theshock absorbing drive assembly 1.

As reflected in FIG. 6A, one preferred use of the tool 1 is in thebottom hole assembly immediately above the drill bit 30. Otherconfigurations which may be used include placing the tool 1 in themiddle of the BHA as shown in FIG. 6B above drill collars 29 which areconnected to the drill bit 30. Since the tool 1 allows independentlongitudinal loading, it may be used in conjunction with other down-holetools such as jars and accelerators, which depend on longitudinalmovement or manipulation of the drill string for their actuation.

SUMMARY, RAMIFICATIONS, SCOPE AND INDUSTRAIL APPLICABILITY

Accordingly, it may be readily appreciated that the rotary andlongitudinal shock absorbing apparatus may be used at a variety oflocations in long pendular strings such as in drill strings to provideshock absorbing movement of the tubular string both up and down. Thistool is the first shock absorbing tool permitting longitudinal or axialshocks to be absorbed while maintaining the ability to absorb abnormaltorque, thereby eliminating potential damage to expensive bits,lessening wear on drill string and bottom-hole assemblies.

Although the description above contains many specific details, theseshould not be construed as limiting the scope of the invention but asmerely providing illustrations of some of the presently preferredembodiments of this invention. The foregoing disclosure and descriptionof the invention are explanatory thereof, and various changes in thesize, shape, and materials as well as in the details of the illustratedconstruction may be made without departing from the spirit of theinvention.

I claim the following:
 1. A rotational and longitudinal shock absorberfor use in a drill string comprising: a mandrel for connection to adrill string and providing external splines, a cylinder telescopicallyengaging said mandrel and having threads formed on the interior surface,seal means between the mandrel and the cylinder to form a chamberbetween an exterior surface of the mandrel and an interior surface ofthe cylinder, a torque cylinder formed with internal splines on theinterior surface and external threads formed on the exterior, saidinterior splines engaging the splines on the mandrel and the exteriorthreads engaging the threads on the interior of the cylinder, resilientmeans carried on said mandrel, engaging a torque sleeve to resist thelongitudinal movement of the torque sleeve in the interior of thecylinder and engaging said mandrel to resist the longitudinal movementof the mandrel within the cylinder.
 2. The invention of claim 1 whereinsaid resilient means includes a plurality of springs having differingcompression coefficients to progressively resist movement of the mandreland the torque sleeve into the cylinder.
 3. A rotary and longitudinalshock absorbing apparatus comprising: a mandrel providing means forconnection to a drill string and external splines, a cylindertelescopically engaging said mandrel and providing means for threadedengagement to a drill bit, seal means forming a hydraulic seal betweenan outer surface of said mandrel and an inner surface of cylinder, atorque sleeve having internal splines for engagement of the splines onsaid mandrel and external threads for engagement of threads on thecylinder, torque-resisting spring means engaging the torque sleeve and ashoulder in the cylinder providing compressive resisting force uponrotational movement of the cylinder relative to said mandrel,longitudinal-movement resisting spring means carried on a shoulder inthe cylinder providing compressive resisting force upon longitudinalmovement of the cylinder relative to said mandrel.
 4. The invention ofclaim 3 wherein the torque-resisting spring means includes a Bellevillespring arrangement slidingly engaging the end of the torque sleeve. 5.The invention of claim 3 wherein the longitudinal-movement resistingspring means includes a plurality of springs slidingly engaging saidmandrel.
 6. The invention of claim 3 wherein said sealed fluid chamberis partially filled with an incompressible fluid and pressure balancedto both pump pressure and to external hydrostatic pressure by portspermitting communication of fluids on each side of the seal means.